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IRIS Update Provides Another Perspective on Existing and Emerging Contaminants

EPA’s Integrated Risk Information System (IRIS) just released information on their priority for upcoming assessments.  For drinking water, IRIS risk assessments provide basic health risks for existing and emerging contaminants that support the development of the Maximum Contaminant Level Goal (MCLG) for new rules or the reconsideration of MCLGs under the Six Year Review of existing regulations.  So, while these are pretty far removed from our regulatory MCLs, the IRIS assessments as they roll out, give some indication of where future drinking water rules might be headed.

This week’s announced list of priority assessments includes many contaminants that are familiar to state drinking water programs.  A public draft for inorganic arsenic is expected in the second quarter of 2020.  A significant change in the risk assessment could influence the next Six Year Review which will be completed in 2023.  Also projected for 2020 is the assessment for chromium VI.  EPA has been considering regulation for chromium VI for many years and a new IRIS assessment could influence their final decision.   Another regulated group of contaminants scheduled for an assessment in 2021 is PCBs.  Here again, major changes in the assessment could influence the Six Year Review.   Other contaminants with draft assessments projected in the next few years include mercury salts and methylmercury.

PFAS have also generated interest from IRIS, although specific dates for assessment release are all “TBD”.  The Program Outlook lists five specific compounds that will be subject to risk assessment.  These include Perfluorononanoic Acid (PFNA), Perfluorobutanoic Acid (PFBA), Perfluorohexanoic Acid (PFHxA), Perfluorohexane Sulfonate (PFHxS), and Perfluorodecanoic Acid (PFDA).  Certainly, if EPA goes down the road of regulating PFAS, this risk information will be extremely valuable.  However, with no projected dates, it remains to be seen whether the assessment will be available when EPA needs it for a drinking water regulatory action.

The December 2018 IRIS Program Outlook can be accessed here.  To keep up with these future assessments and any that are active now, visit EPA’s IRIS web page.